Method for producing display device, and display device

The disclosure relates to a method for manufacturing a display device and a display device.

It is known that a quantum dot layer functioning as a layer for emitting light in a quantum dot light emitting diode (QLED) display device is formed by lift-off.

PTL 1: JP 2017-121787 A

NPL 1: Bull. Chem. Soc. Jpn. 2019, 92, 952 to 960, ACS Nano 2019, 13, 4, 3823 to 3829 NPL 2: Nature 2020, 586, 385 to 389

When a quantum dot layer is formed by lift-off, the film thickness of the quantum dot layer may become non-uniform.

(a) a first functional group capable of being coordinated to the oxide, (b) a second functional group that is cleaved by being irradiated with ultraviolet light to generate any one of an amino group, a carboxyl group, a thiol group, and a selenol group, irradiating at least a part of the first solution applied to the substrate with first ultraviolet light, and applying a solution containing halogenated first quantum dots to a portion irradiated with the first ultraviolet light in the irradiating at least a part of the first solution applied to the substrate to form a first quantum dot layer. A method for manufacturing a display device according to an aspect of the disclosure includes applying a first solution containing (a) and (b) to a substrate containing an oxide,

A display device according to an aspect of the disclosure includes a substrate containing an oxide, a first bonding functional group capable of bonding to the oxide, a second bonding functional group bonded to the first bonding functional group via a carbon chain, the second bonding functional group being any one of an amino group, a carboxyl group, a thiol group, and a selenol group, and a quantum dot layer, in which the quantum dot layer includes halogen and quantum dots each bonded to the second bonding functional group and the halogen.

According to an aspect of the disclosure, a film thickness of a quantum dot layer can be suppressed from becoming non-uniform.

Embodiments of the disclosure will be described below. Note that, for convenience of description, members having the same functions as the members described earlier may be denoted by the same reference numerals and signs, and the description thereof will not be repeated.

1 FIG. 101 is a block diagram illustrating a schematic configuration of a display deviceaccording to the disclosure.

101 1 2 3 4 101 The display deviceincludes a substrate, a first bonding functional group, a second bonding functional group, and a quantum dot layer. In addition, the display deviceincludes electrodes (an anode electrode and a cathode electrode), and if necessary, a carrier transport layer (a hole transport layer and/or an electron transport layer), and the like, which are not illustrated or described because they are not closely related to the point of the disclosure.

1 5 1 1 5 The substratecontains an oxide. As a specific example, the substrateis a metal oxide semiconductor substrate. The substratecan be constituted by forming an oxide film on a base material. Examples of the oxideconstituting the oxide film include zinc oxide, tin oxide, titanium oxide, indium oxide, copper oxide, molybdenum oxide, gallium oxide, nickel oxide, and a mixture of two or more of them. Examples of a method for forming the oxide film include a sputtering method, a sol-gel method, and a nanoparticle application method.

2 5 1 The first bonding functional groupis a functional group that can bond to the oxidecontained in the substrate.

3 2 3 The second bonding functional groupis a functional group bonded to the first bonding functional groupvia a carbon chain. The second bonding functional groupis any one of an amino group, a carboxyl group, a thiol group, and a selenol group.

4 4 6 7 3 6 The quantum dot layerfunctions as a layer that emits light in the QLED display device. The quantum dot layerincludes halogenand quantum dotseach bonded to the second bonding functional groupand the halogen.

101 1 7 1 7 7 6 In the display device, a part of a surface of the substratemay be covered with the quantum dots, the surface of the substrateand each quantum dotmay be bonded to the same low molecule, and 80% or more of a surface of each of the quantum dotsmay be covered with the halogen.

2 FIG. 101 is diagrams illustrating a method for manufacturing the display deviceaccording to a first embodiment of the disclosure, and illustrates a first step, a second step, and a third step.

8 1 5 1 1 FIG. (a) A first functional group that can be coordinated to the oxide(see) contained in the substrate (b) A second functional group that is cleaved by being irradiated with ultraviolet light to generate any one of an amino group, a carboxyl group, a thiol group, and a selenol group In the first step, a first solutioncontaining (a) and (b) is applied to the substrate.

8 8 1 8 The first solutioncontains, for example, alcohol and molecules each containing the first functional group and the second functional group, and a concentration of the molecules in the first solutionis 0.1 mmol/l or more. Furthermore, in the first step, the substrateapplied with the first solutionis heated at 100° C. for 1 hour, and then subjected to ultrasonic cleaning in alcohol for 5 minutes, and then dried.

“Cleavage” means that a chemical bond is broken.

8 1 9 8 1 10 11 10 9 9 11 9 2 FIG. In the second step, at least a part of the first solutionapplied to the substrateis irradiated with first ultraviolet light. In, a part of the portion applied with the first solutionof the substrateis covered with a photomask, and a first ultraviolet light irradiation areathat is a portion not covered with the photomaskis irradiated with the first ultraviolet light. A wave length of the first ultraviolet lightis, for example, 300 nm or more and 400 nm or less. Irradiation time of the first ultraviolet light irradiation areawith the first ultraviolet lightis, for example, three minutes.

1 After the second step, the substrateis immersed in chloroform and subjected to ultrasonic cleaning for one minute.

12 7 11 9 4 7 7 12 11 1 12 4 7 4 7 a a a a a a 1 FIG. In the third step, a solutioncontaining halogenated first quantum dotsis applied to a portion (first ultraviolet light irradiation area) irradiated with the first ultraviolet lightin the second step to form a first quantum dot layer. In the halogenated first quantum dots, for example, a surface of each of the first quantum dotsis halogenated. Examples of a method for applying the solutionto the first ultraviolet light irradiation areainclude spin coating. Furthermore, in the third step, the substrateapplied with the solutionis allowed to stand for 10 minutes and then washed with a solvent such as acetone. The first quantum dot layerand the first quantum dotsare included in the quantum dot layerand the quantum dots(see), respectively.

4 4 a a According to the above configuration, the first quantum dot layercan be formed without applying lift-off, and thus the film thickness of the first quantum dot layercan be suppressed from becoming non-uniform.

The first functional group preferably contains any one of a phosphonyl group, a carboxyl group, and a silanol group. According to the above configuration, the first functional group that suitably satisfies (a) can be realized.

The second functional group preferably contains an ester bond. According to the above configuration, the second functional group that suitably satisfies (b) can be realized.

8 7 4 9 4 a a a The first solutionpreferably does not contain an organic ligand including a functional group that is coordinated to each of the halogenated first quantum dots. According to the above configuration, the first quantum dot layeris strongly fixed by chemical bonding to the portion irradiated with the first ultraviolet lightin the second step, and thus the first quantum dot layeris less likely to be detached in a subsequent step.

3 FIG. 7 a is diagrams illustrating a method for producing first quantum dotseach having a halogenated surface.

7 13 14 14 15 a First, the first quantum dotseach protected by a general organic ligandare dispersed in a non-polar solvent to form a first liquid. Examples of the non-polar solvent include hexane and octane. Metal halide of 0.1 mol/l is dissolved in an aprotic polar solvent immiscible with the first liquidto prepare a second liquid. Examples of the polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and acetonitrile. Examples of the metal halide include zinc bromide.

14 15 7 14 15 16 15 15 7 16 17 7 17 7 7 18 a a a a a Subsequently, the first liquidand the second liquidare mixed and stirred while being separated from each other. The stirring time is, for example, 12 hours. After confirming that the first quantum dotshave moved from the first liquidside to the second liquidside, a non-polar solventmiscible with the second liquidis added to the second liquidto precipitate the first quantum dots. Examples of the non-polar solventinclude toluene and ethyl acetate. By being dispersed in a polar solvent, the first quantum dotseach having the halogenated surface are obtained. Examples of the polar solventinclude DMSO and DMF. In other words, the first quantum dotseach having the halogenated surface are the first quantum dotseach protected by a halogen ligand.

14 7 13 15 14 7 14 15 7 a a a That is, it is preferable that (1) the first liquidin which the first quantum dotseach coordinated with the organic ligandare dispersed in a non-polar solvent and (2) the second liquidimmiscible with the first liquidand containing the aprotic polar solvent and the metal halide be mixed, and the halogenated first quantum dotsbe taken out from the liquid obtained by mixing the first liquidand the second liquid. According to the above configuration, the halogenated first quantum dotscan be produced.

8 Note that the first solutioncontains, in addition to the first functional group and the second functional group, a third functional group required for absorbing the ultraviolet light.

4 FIG. 19 20 21 8 is diagrams illustrating a first example, a second example, and a third example of a combination of a first functional group, a second functional group, and a third functional groupcontained in the first solution.

4 FIG. 4 FIG. 8 19 20 21 n: 1 or more and 10 or less m: 1 or more and 2 or less 2 X: oxygen atom (O), sulfur atom(S), NH, or CH R: a functional group selected from hydrogen, fluorine, an alkyl group, a phenyl group, a hydroxyl group, an alkoxy group, a nitro group, a cyano group, an amino group, and a sulfonyl group In each example in, in the first solution, the first functional group, the second functional group, and the third functional groupare bonded to each other via an alkyl chain. The alkyl chain may be branched. In each example in, the following can be said.

21 21 Depending on a structure of the third functional group, a wavelength of the ultraviolet light that can be absorbed by the third functional groupcan be controlled.

101 8 1 9 1 1 9 12 7 6 1 7 9 a a 1 FIG. A patterning method of the display devicemay be a method in which the first solutioncoordinated to the substrateand having a part of molecular structure being decomposed to expose any one of the thiol group, the carboxyl group, and the amino group when irradiated with the first ultraviolet lightis applied to the entirety of the substrate, only a part of the substrateis irradiated with the first ultraviolet light, the solutioncontaining the first quantum dotshaving the surface covered with the halogen(see) by 80% or more is applied to the entirety of the substrate, and the first quantum dotsare deposited only on the portion irradiated with the first ultraviolet light.

Hereinafter, the significance of halogenating the surface of each of the quantum dots will be discussed.

It was confirmed by the following method that the quantum dots each having the surface covered with halogen rapidly underwent ligand exchange.

CdSe/ZnS quantum dots covered with oleic acid were prepared so as to obtain a hexane solution of 2 mg/ml. A DMSO solution of zinc bromide of 0.2 mol/ml and ammonium acetate of 0.01 mol/ml were prepared. When these were mixed in equal amounts, the mixture was separated into two layers, but when the mixture was vigorously stirred for a certain period of time (for example, 12 hours), the quantum dots moved to the DMSO solution side that was a lower layer. Impurities were removed by precipitating the quantum dots by adding ethyl acetate and toluene dropwise to the DMSO solution. A solution in which the quantum dots each having the surface almost entirely covered with bromide ions were dispersed in the polar solvent was obtained by dispersing the precipitate in DMF.

5 FIG. 5 FIG. is a table comparing Example, Comparative Example 1, and Comparative Example 2.also illustrates chemical formulae of dodecylamine and diethylaminoethanethiol.

The quantum dots can be either polar or non-polar depending on the ligand on the surface of each of the quantum dots. However, when the quantum dots are coordinated to the substrate on which thiol or the like is exposed, the non-polar quantum dots dispersed in the non-polar solvent cannot be coordinated to the substrate because the solution is repelled by a highly hydrophilic substrate on which a functional group having polarity is exposed. Thus, the quantum dots according to the disclosure need to be dispersed in a solvent having high polarity.

5 FIG. 5 FIG. In order to produce quantum dots each having an exposed polar plane that is dissolved in the polar solvent, a ligand can be applied that is coordinated to each of the quantum dots and allow the quantum dots to be dissolved in the polar solvent. Examples of the ligand include halogen, a sulfide ion, and diethylaminoethanethiol that is an organic ligand having high polarity. Their applicability to the quantum dots will be confirmed. In the table in, an example in which the ligand coordinated to each of the quantum dots is halogen is shown as Example, an example in which the ligand coordinated to each of the quantum dots is a sulfide ion is shown as Comparative Example 1, and an example in which the ligand coordinated to each of the quantum dots is diethylaminoethanethiol is shown as Comparative Example 2 (see columns of compounds on a quantum dot surface). In addition,shows raw materials of the ligands in the examples, respectively (see columns of the raw materials).

In Example, zinc bromide was dissolved in a DMF solvent to finally obtain quantum dots subjected to ligand substitution with bromine ions, and the quantum dots were dispersed in DMF. On the other hand, in Comparative Examples 1 and 2, sodium sulfide and diethylaminoethanethiol were dissolved in DMF, respectively, instead of zinc bromide in Example, and each of the compounds described in the columns of compounds on the quantum dot surface was finally coordinated to each of the quantum dots and dispersed in DMF.

5 FIG. When dodecylamine is dissolved in octane that is a non-polar solvent and stirred while being separated from the DMF solution of the quantum dots into two layers (DMF in the lower layer and octane in the upper layer), each ligand is substituted by dodecylamine, and thus the quantum dots exhibit non-polarity. As a result, the quantum dots move to the octane side that is the upper layer. The ease of substitution of each ligand with the organic ligand can be quantified from time until the quantum dots completely move to the octane side. The time until the quantum dots completely move to the octane side is shown in columns of time until the quantum dots move to a hydrophobic layer containing the organic ligand in.

Halogen>Organic ligand exhibiting polarity when coordinated to each of the quantum dots>Sulfide ion The quantum dots coordinated with bromide ions completely moved to the octane side in 10 seconds, whereas the quantum dots coordinated with sulfide ions did not move and the quantum dots coordinated with diethylaminoethanethiol took 12 hours to move. Accordingly, the ease of substitution of each ligand with the organic ligand is considered to be in the following order.

A reaction rate in the solution is also related to a reaction rate with the organic ligand on the oxide substrate, and thus the quantum dots are rapidly fixed to the substrate in Example. Thus, Example is considered to be suitable.

As a method for preparing a display device patterned by a solution process, there are an ink-jet method in which a solution is applied only to a specific portion and a photolithography method. The inkjet method has a limit in definition, and thus it is not suitable for a display device requiring high definition. The photolithography method enables high definition, and thus QLED display devices using various methods have been studied. As a method for manufacturing a QLED display device using the photolithography method, there is a method in which a photoresist that is cured by light irradiation and the quantum dots are mixed and cured. However, in this method, a ratio of a resist material in the quantum dot layer is large, and thus luminous efficiency and durability of the quantum dot layer are low. There is also known a method in which the photoresist is patterned on a sacrificial layer, a hole is formed in a part of the sacrificial layer by plasma etching, the quantum dots are applying to the entire surface, and then the sacrificial layer is dissolved and removed with a solution, and thus the quantum dot layer is patterned. However, in this method, there is a problem that the thickness of the quantum dot layer becomes non-uniform, and the removed quantum dots and the sacrificial layer are mixed in the same solvent, and thus it is difficult to reuse the quantum dots, and the material utilization efficiency is low.

Thus, in the present method, by patterning the substrate side with light, the quantum dots are coordinated to only a part, and other impurities are not contained in the removed quantum dot solution, and thus the quantum dots can be reused and the material utilization efficiency is high. Further, since the patterning is performed by the light irradiation, the high definition can be achieved.

According to the present embodiment, the substrate is covered with a monomolecular film that exposes a functional group to which the quantum dots are coordinated by the light irradiation. Most (80% or more) of the surface of each of the quantum dots in the solution is covered with halogen, and thus the quantum dots are rapidly coordinated to the substrate.

According to the present embodiment, it is possible to solve the problems that the light emission is adversely affected by the contact between the photoresist and the quantum dots and the photoresist remains on the substrate.

There is known a technique of patterning a monomolecular film having a photocleavable structure by chemically modifying the monomolecular film with a fluorescent substance (see NPL 1). However, an application in which the fluorescent substance is simply replaced with the quantum dots with respect to the technique is difficult. This is because the quantum dots are each usually covered with the organic ligand and thus dissolved in the non-polar solvent, and the surface exposed by cleavage is polar, and thus wettability of the polar surface with the non-polar solvent is not good, which causes a problem that the quantum dots cannot be applied well. Thus, it is effective to make the quantum dots soluble in the polar solvent by substituting halogen for the organic ligand of the quantum dots so that the quantum dots can be applied.

A method is known in which halogen is substituted for a part of the quantum dot surface covered with the organic ligand and the substituted quantum dots are dispersed in the non-polar solvent (see NPL 2). However, when 80% or more of the quantum dot surface is modified with halogen by the above-described method or the like, the quantum dots are easily dissolved in the polar solvent.

6 FIG. 101 is diagrams illustrating a method for manufacturing the display deviceaccording to a second embodiment of the disclosure, and illustrates a fourth step and a fifth step.

2 FIG. 6 FIG. 8 1 9 22 1 8 9 4 9 4 23 24 23 22 22 24 22 a a The fourth step is a step after the third step (see). In the fourth step, a portion that is at least a part of the first solutionapplied to the substrateand not irradiated with the first ultraviolet lightis irradiated with second ultraviolet light. In, among the portion of the substrateapplied with the first solution, the portion irradiated with the first ultraviolet light(thus, the portion where the first quantum dot layeris formed) and a part of the portion not irradiated with the first ultraviolet light(thus, the portion where the first quantum dot layeris not formed) are covered with a photomask, and a second ultraviolet light irradiation areathat is a portion not covered with the photomaskis irradiated with the second ultraviolet light. A wave length of the second ultraviolet lightis, for example, 300 nm or more and 400 nm or less. Irradiation time of the second ultraviolet light irradiation areawith the second ultraviolet lightis, for example, three minutes.

25 7 24 22 4 7 7 25 24 4 7 4 7 b b b b b b 1 FIG. In the fifth step, a solutioncontaining halogenated second quantum dotsis applied to a portion (second ultraviolet light irradiation area) irradiated with the second ultraviolet lightin the fourth step to form a second quantum dot layer. In the halogenated second quantum dots, for example, a surface of each of the second quantum dotsis halogenated. Examples of a method for applying the solutionto the second ultraviolet light irradiation areainclude spin coating. The second quantum dot layerand the second quantum dotsare included in the quantum dot layerand the quantum dots(see), respectively.

4 4 7 7 a b a b According to the above configuration, the first quantum dot layerand the second quantum dot layercan be separately formed, and thus the first quantum dotsand the second quantum dotscan be separately patterned.

6 FIG. 1 FIG. 8 1 9 22 26 27 28 7 26 4 7 7 4 7 4 7 c c c c c c In, the following steps are further performed after the fifth step. That is, a portion that is at least a part of the first solutionapplied to the substrateand is not irradiated with any of the first ultraviolet lightand the second ultraviolet lightis irradiated with third ultraviolet lightby using a photomask. Then, a solutioncontaining halogenated third quantum dotsis applied to a portion irradiated with the third ultraviolet lightto form a third quantum dot layer. In the halogenated third quantum dots, for example, a surface of each of the third quantum dotsis halogenated. The third quantum dot layerand the third quantum dotsare included in the quantum dot layerand the quantum dots(see), respectively.

7 FIG. 101 is diagrams illustrating a method for manufacturing the display deviceaccording to a third embodiment of the disclosure.

29 7 4 7 4 30 7 29 4 4 a a b a b a b. After the third step, a second solutioncontaining (A) the halogenated first quantum dotsconstituting the first quantum dot layerand (B) a functional group that can be coordinated to each of the halogenated second quantum dotsmay be applied to at least the first quantum dot layer, and a solutioncontaining the halogenated second quantum dotsmay be applied to a portion where the second solutionis applied to the first quantum dot layerto form the second quantum dot layer

4 4 7 4 1 7 7 a b a a a b According to the above configuration, when a layered structure of the first quantum dot layerand the second quantum dot layeris formed, the first quantum dotsconstituting the first quantum dot layercan be prevented from being detached from the substrate. When a material of the first quantum dotsand a material of the second quantum dotsare the same, the layered structure is suitable for forming a quantum dot layer (corresponding to the layered structure) having a large film thickness.

29 Examples of the second solutioninclude an organic ligand solution, typified by ethanedithiol, including two or more functional groups that can be coordinated to two or more quantum dot surfaces.

101 7 7 29 a b In the display deviceaccording to the present embodiment, an interval between the first quantum dotsand the second quantum dotsis preferably 3 nm or less. The length of the organic ligand contained in the second solutionis preferably 20 carbon atoms or less, and more preferably 10 carbon atoms or less.

4 4 1 FIG. In the above, the example is described in which the quantum dot layer(see) is formed as the layered structure of two layers. On the other hand, the quantum dot layermay be formed as a layered structure of three or more layers by repeating the steps according to the present embodiment.

8 FIG. 101 is diagrams illustrating a method for manufacturing the display deviceaccording to a fourth embodiment of the disclosure.

31 7 1 4 31 a a Before the fifth step, a detachment preventing agentfor preventing the first quantum dotsfrom being detached from the substratemay be applied to at least the first quantum dot layer. Here, the detachment preventing agentis applied before the fourth step.

4 7 4 1 b a a According to the above configuration, when the second quantum dot layeris formed, the first quantum dotsconstituting the first quantum dot layercan be prevented from being detached from the substrate.

31 Examples of the detachment preventing agentinclude a hydrophobic polymer. The hydrophobic polymer may be an insulator or may have a carrier transport property.

31 31 1 22 31 1 1 When the detachment preventing agentis applied before the fourth step, the detachment preventing agentis preferably peeled off from the substrateby being irradiated with the second ultraviolet lightin the fourth step. In this case, it is preferable that the detachment preventing agentcan be washed away from the substrateby washing the substratewith a solvent after the peel off.

9 FIG. 4 101 is a schematic view illustrating a cross section of the quantum dot layerof the display device.

101 101 32 4 33 4 101 4 In the display devicemanufactured by the method for manufacturing the display deviceaccording to each of the embodiments described above, an average film thickness of an end portionof the quantum dot layercan be 80% or more and 120% or less of an average film thickness of a central portionof the quantum dot layer. According to the above configuration, the display deviceis a display device in which the film thickness of the quantum dot layeris uniform.

4 32 33 4 32 4 34 4 35 4 33 4 35 4 34 4 9 FIG. Referring to the cross section of the quantum dot layerillustrated in, the end portionand the central portionof the quantum dot layercan be defined as follows, for example. The end portionof the quantum dot layeris a portion within 100 nm in a direction from an outer edgeof the quantum dot layertoward a centerof the quantum dot layer. The central portionof the quantum dot layeris a portion within 50 nm in a direction from the centerof the quantum dot layertoward the outer edgeof the quantum dot layer.

32 4 32 4 33 4 33 4 The average film thickness of the end portionof the quantum dot layeris obtained by selecting two or more measurement points from the end portionof the quantum dot layer, measuring the film thickness at each measurement point with a cross-sectional transmission electron microscopy (TEM), and addition-averaging the measurement results. The average film thickness of the central portionof the quantum dot layeris obtained by selecting two or more measurement points from the central portionof the quantum dot layer, measuring the film thickness at each measurement point with a cross-sectional TEM, and addition-averaging the measurement results.

(a) a first functional group capable of being coordinated to the oxide, (b) a second functional group that is cleaved by being irradiated with ultraviolet light to generate any one of an amino group, a carboxyl group, a thiol group, and a selenol group, irradiating at least a part of the first solution applied to the substrate with first ultraviolet light, and applying a solution containing halogenated first quantum dots to a portion irradiated with the first ultraviolet light in the irradiating at least a part of the first solution applied to the substrate to form a first quantum dot layer. A method for manufacturing a display device according to a first aspect of the disclosure includes applying a first solution containing (a) and (b) to a substrate containing an oxide,

According to the above configuration, the first quantum dot layer can be formed without applying lift-off, and thus the film thickness of the first quantum dot layer can be suppressed from becoming non-uniform.

In the method for manufacturing a display device according to a second aspect of the disclosure, according to the first aspect, the first functional group contains any one of a phosphonyl group, a carboxyl group, and a silanol group.

According to the above configuration, the first functional group that suitably satisfies (a) can be realized.

In the method for manufacturing a display device according to a third aspect of the disclosure, according to the first or second aspect, the second functional group contains an ester bond.

According to the above configuration, the second functional group that suitably satisfies (b) can be realized.

In the method for manufacturing a display device according to a fourth aspect of the disclosure, according to any one of the first to third aspects, the first solution does not contain an organic ligand including a functional group that is coordinated to each of the halogenated first quantum dots.

According to the above configuration, the first quantum dot layer is strongly fixed to the portion irradiated with the first ultraviolet light in the irradiating at least a part of the first solution applied to the substrate, and thus the first quantum dot layer is less likely to be detached in a subsequent step.

In the method for manufacturing a display device according to a fifth aspect of the disclosure, according to any one of the first to fourth aspects, (1) a first liquid in which first quantum dots each coordinated with an organic ligand are dispersed in a non-polar solvent and (2) a second liquid immiscible with the first liquid and containing an aprotic polar solvent and metal halide are mixed, and the halogenated first quantum dots are taken out from a liquid obtained by mixing the first liquid and the second liquid.

According to the above configuration, the halogenated first quantum dots can be produced.

The method for manufacturing a display device according to a sixth aspect of the disclosure, according to any one of the first to fifth aspects, further includes irradiating a portion that is at least a part of the first solution applied to the substrate and is not irradiated with the first ultraviolet light with second ultraviolet light after the applying a solution containing halogenated first quantum dots, and applying a solution containing halogenated second quantum dots to the portion irradiated with the second ultraviolet light in the irradiating a portion that is at least a part of the first solution applied to the substrate and is not irradiated with the first ultraviolet light to form a second quantum dot layer.

According to the above configuration, the first quantum dot layer and the second quantum dot layer can be separately formed, and thus the first quantum dots and the second quantum dots can be separately patterned.

In the method for manufacturing a display device according to a seventh aspect of the disclosure, according to the sixth aspect, before the applying a solution containing halogenated second quantum dots, a detachment preventing agent for preventing the halogenated first quantum dots from being detached from the substrate is applied to at least the first quantum dot layer.

According to the above configuration, when the second quantum dot layer is formed, the first quantum dots constituting the first quantum dot layer can be prevented from being detached from the substrate.

In the method for manufacturing a display device according to an eighth aspect of the disclosure, according to any one of the first to seventh aspects, after the applying a solution containing halogenated first quantum dots, a second solution containing (A) the halogenated first quantum dots constituting the first quantum dot layer and (B) a functional group capable of being coordinated to each of the halogenated second quantum dots are applied to at least the first quantum dot layer, and a solution containing the halogenated second quantum dots is applied to a portion where the second solution is applied to the first quantum dot layer to form a second quantum dot layer.

According to the above configuration, when a layered structure of the first quantum dot layer and the second quantum dot layer formed, the first quantum dots constituting the first quantum dot layer can be prevented from being detached from the substrate. When a material of the first quantum dots and a material of the second quantum dots are the same, the layered structure is suitable for forming a quantum dot layer (corresponding to the layered structure) having a large film thickness.

A display device according to a ninth aspect of the disclosure includes a substrate containing an oxide, a first bonding functional group capable of bonding to the oxide, a second bonding functional group bonded to the first bonding functional group via a carbon chain, the second bonding functional group being any one of an amino group, a carboxyl group, a thiol group, and a selenol group, and a quantum dot layer, in which the quantum dot layer includes halogen and quantum dots each bonded to the second bonding functional group and the halogen.

According to the above configuration, the quantum dot layer can be formed without applying lift-off, and thus a display device in which a film thickness of the quantum dot layer is uniform.

In the method for manufacturing a display device according to a tenth aspect of the disclosure, according to the ninth aspect, an average film thickness of an end portion of the quantum dot layer is 80% or more and 120% or less of an average film thickness of a central portion of the quantum dot layer.

According to the above configuration, the display device is a display device in which the film thickness of the quantum dot layer is uniform.

The disclosure is not limited to each of the embodiments described above, and various modifications may be made within the scope of the claims. Embodiments obtained by appropriately combining technical approaches disclosed in each of the different embodiments also fall within the technical scope of the disclosure. Furthermore, novel technical features can be formed by combining the technical approaches disclosed in each of the embodiments.